Hashimoto’s disease

Thyroid gland

The thyroid is an endocrine gland located on the anterior aspect of the neck, just below the larynx. Anteriorly, the infrahyoid muscles cover the gland. Lateral to the thyroid gland is the sternocleidomastoid muscle. Posteriorly, it is fixed to the tracheal and cricoid cartilage and cricopharyngeus muscle. It is attached firmly to the underlying trachea, which causes its movement with swallowing. It gains its blood supply from the superior and inferior thyroid arteries, which arise from the external carotid, and thyrocervical trunk respectively. Its drainage is from the superior, middle and inferior thyroid veins which drain into the internal jugular (superior and middle) and brachiocephalic vein (inferior).

The thyroid gland produces two hormones, thyroxine (T4) and triiodothyronine (T3) that influence metabolism and affect breathing, heart rate, skin dryness, body temperature, weight, menstrual cycles, muscle strength, cholesterol levels, the nervous system, and prenatal development.

Signs and symptoms

Signs and symptoms are not always present during the initial course of the disease. As the condition slowly progresses the following symptoms can become more evident:

• Weight gain
• Poor appetite
• Cold intolerance
• Shortness of breath
• Hoarse voice
• Fatigue
• Muscle pain
• Joint pain and stiffness
• Dyspepsia
• Constipation (reduced bowel movements)
• Heavy or irregular menstrual periods
• Problems becoming pregnant
• Psychiatric problems: Depression
• Poor memory
• Bradycardia
• Thinning, dry hair
• Dry, coarse skin
• Cold extremities
• Myxedema
• Swollen hands and feet
• Thick brittle nails
• Puffy face
• Decreased reflexes

The main sign of disease could be goitre formation, which is a swelling of the neck resulting from enlargement of the thyroid gland. The goitre if present is firm and lobulated in Hashimoto’s thyroiditis. The size of the goitre usually can be classified into grades:

Grade 0 – No presence of goitre is found. It is impalpable and invisible.

Grade 1 – Neck thickening is palpable, it moves upwards during swallowing and is not yet visible in normal position of the neck.

Grade 2 – Neck swelling is visible in normal neck position and also palpable.

Risk factors

Hashimoto’s is usually seen in women. It occurs at any age but more commonly seen between ages of 30-50. A family history of thyroid disease can increase the risk of developing Hashimoto’s disease. The gene HLA-DR5 is strongly associated with it. Environmental factors such as exposure to excessive iodine from certain drugs may contribute. And those exposed to radiation can be at higher risk.

Investigations

The three most common tests for diagnosing Hashimoto’s are free thyroxine T4 hormone test, thyroid-stimulating hormone test and the anti-thyroid antibodies tests.

This blood test is checking for free T4 hormone levels and is used as an initial diagnostic step. In Hashimoto’s the thyroid will not be making enough thyroid hormone.

Thyroid-stimulating hormone test is another useful blood test. If thyroid-stimulating hormone is above the normal range this can be an indication of Hashimoto’s disease. Thyroid-stimulating hormone is produced by the pituitary gland located in the brain. If the pituitary senses a reduction in thyroid hormone, it will initiate increased release of thyroid-stimulating hormone to try stimulating the production of thyroid hormone from the thyroid.

When immune cells attack your thyroid gland, antibodies are produced. Anti-thyroid antibodies tests help to detect presence of them in the body and measure the levels.

The most common antibodies to look for in autoimmune thyroid disease are the thyroid peroxidase antibody (anti-TPO) and anti-microsomal antibody.

Another useful antibody is called the anti-thyroglobulin antibody (TGAb), this targets thyroglobulin which is a form of thyroid hormone when it is being stored. The characteristic histological features of Hashimoto’s thyroiditis include atrophied thyroid follicle with Hurthle cells, metaplastic follicular epithelium and abundant lymphoplasmacytic infiltrate. There may be varying degree of fibrosis.

Management

Hashimoto’s disease can be managed with thyroid hormone replacement such as levothyroxine. In most cases, treatment is lifelong thyroid replacement therapy. Monitoring of dosages is key as excessive amounts of thyroid hormone can lead to cardiac problems such as arrhythmias. The role of surgery is only when the swelling is very large and causes symptoms of compression.

Complications

This condition can lead to complications including the higher risk of developing other autoimmune diseases such as type 1 diabetes, Addison’s disease, Grave’s disease, rheumatoid arthritis, premature ovarian failure, systemic lupus erythematosus, pernicious anaemia, and vitiligo.

Due to the increased cholesterol levels, Hashimoto’s can put you at higher risk of cardiac problems. Psychiatric disorders may occur, such as depression and with the progression of the disease can become more severe.

In long-term Hashimoto’s, myxoedema coma is a life-threatening and rare complication of the disease. Patients experience extreme cold intolerance and becoming increasingly drowsy, lethargic and eventually unconscious. This can be triggered by infection or sedatives.

A very rare complication of having Hashimoto’s disease is developing an increased risk of thyroid lymphoma. The majority of thyroid lymphoma cases are classified as non-Hodgkin’s B cell lymphomas. It will manifest with hoarseness of voice and dysphagia symptoms. On examination a firm, painless thyroid will be palpable and the presence of lymphadenopathy. If detected early, it is treatable and therefore is important to be checked in patients with Hashimoto’s.